Ladder adapter device

Abstract

A device for adapting a ladder to be supported on uneven ground comprises a tubular guide rigidly connected to an upright of the ladder, a hollow slide received in the guide and bearing a toothed rack and having a longitudinal slot opposite the rack, and a pawl borne by the tubular guide and adapted to engage a tooth of the rack to support the slide at a chosen position in the guide.

Description

This invention relates to a ladder adapter device for allowing a ladder to be supported on uneven ground such as on different steps of stairs while maintaining a correct position with full support on the feet of both uprights.

It is a main object of the invention to provide an adapter device of the kind set forth above, which can be easily and readily operated to adapt itself automatically to the ground.

It is a further object of the invention to form such a device in such a way that it can be either built into a ladder to be an integral part thereof or, alternatively, fitted to an existing ladder without altering its construction.

The invention achieves the above and other objects, as will appear from its specification, by providing a ladder adapter device comprising: a tubular guide adapted to be rigidly connected to the lower end of an upright of the ladder; a pawl pivotally mounted on the guide; a hollow slide received in the guide and having a longitudinal slot through which the pawl can penetrate the slide; a rack rigidly connected to an inner surface of the hollow slide and bearing teeth opposite to the slot; the pawl being operable to engage a tooth of the rack to resist forces tending to move the guide with respect to the slide in a predetermined direction. The invention also provides a ladder fitted with such a device.

The invention is further illustrated by way of example in the following specification describing preferred embodiments thereof, with reference to the accompanying drawings, in which:

FIG. 1 is a partly broken, perspective view of a ladder having a built-in adapter device according to the invention;

Fig. 2 is a broken-away, longitudinal cross-section view taken along line II--II of FIG. 1, in an enlarged scale;

FIG. 3 is a front view of a conventional ladder fitted with a removable adapter device according to the invention.

With reference to FIGS. 1 and 2 of the drawings, a ladder has two rigid uprights 10 and 12, with rungs 14 extending between and being conventionally connected to the uprights. The lower end of upright 10 is fitted with a metal cap 16 which carries a conventional pivoted foot 18 rotatably secured by means of a nut-and-bolt arrangement 20.

Upright 12 is shorter than upright 10 and a tubular guide 22 is fitted onto the lower end of upright 12 and is secured to it by means of nut-and-bolt arrangement 24. A sleeve 21 is rigidly secured, such as by welding, to the wall of the tubular guide 22 and the bottom rung 23 of the ladder has one end received in the sleeve 21, the other end being conventionally supported on the upright 10.

A hollow slide 26 is received within the tubular guide 22 and its lower end carries a pivoted foot 28 similar to foot 18. When the slide 26 is completely retracted in the tubular guide 22, the feet 18 end 28 are at the same level.

The slide 26 has a longitudinal slot 30 extending for the major part of its length. A rack 32 is rigidly secured, such as by welding, on the inner face of the hollow slide opposite to the slot 30, and extends longitudinally for the length of the slot. The rack 32 has teeth with sides at 45.degree. to the longitudinal axis of the hollow slide 26.

The tubular guide 22 has an aperture 34 in its wall adjacent to the slot 30 of the slide 26. Two lugs 36 protrude outwardly near the aperture 34 and support a pivot 38 on which a pawl 40 is rotatably mounted. The pawl 40 is shaped with an end surface 42 such that, when the pawl is rotated counterclockwise on FIG. 2 through the slot 30 until it is stopped by the rack 32, the face 42 can rest flatly against the upper side of one of the teeth of the rack.

An operating lever 44 is integral with the pawl 40 and is so proportioned as to lie against the wall of the tubular guide 22 when the pawl 40 is in the position shown on FIG. 2, with its end face 42 resting against a tooth of the rack. A spring 46 normally maintains the pawl-and-lever combination in this position.

When the ladder is used on even ground, the slide is retracted fully within the tubular guide, by pulling the lever 44 and allowing the ladder to sink around the slide. In this position the ladder can also be carried around without having the slide drop out of the tubular guide, since the spring-loaded action of the side surface of the pawl against the under side of the higher tooth adjacent to it will prevent the slide from dropping.

When the ladder is to be used on uneven ground, it is laid with its fixed foot resting on the higher ground and the movable foot overlying the lower ground. The operating lever 44 is then pulled to withdraw the pawl from engagement with the rack. The slide 26 will then fall down by itself until the foot 28 rests on the ground. The operating lever is then released to allow the pawl 40 to engage a tooth of the rack. When the user climbs the ladder, his weight will improve the engagement between the pawl and the rack and prevent any accidental disengagement.

FIG. 3 shows a conventional ladder 49 having equally long uprights and fitted with a device 50 according to the above description by means of metal bands 52. This arrangement allows a conventional ladder to be provided with an adapter device without altering the construction of the ladder.

The above disclosure of the invention has been given by way of example and is not intended to limit the scope of the invention, which is defined in the appended claims.

Claims

I claim as my invention:

1. An adapter device for a ladder having two uprights and a plurality of rungs, the device comprising:

a tubular guide adapted to be rigidly connected to an upright of the ladder;

a pawl pivotally mounted on the guide;

a hollow slide received in the guide and having a longitudinal slot through which the pawl can penetrate the slide;

a rack rigidly connected to an inner surface of the hollow slide and bearing teeth opposite the slot;

the pawl being operable to engage a tooth of the rack to resist forces tending to move the guide with respect to the slide in a predetermined direction.

2. The device of claim 1, wherein the teeth of the rack have sides at 45.degree. to the longitudinal axis of the rack.

3. The device of claim 1, wherein the tubular guide is apertured and the pawl extends through the aperture and is pivotally mounted on an outer surface of the guide.

4. The device of claim 3, further comprising an operating lever for the pawl, the lever being integral with the pawl.

5. The device of claim 4, wherein the operating lever is adapted to lie along the outer surface of the guide while the pawl engages one of the teeth of the rack.

6. The device of claim 4, further comprising spring means connected to the pawl to urge the pawl in a position where it engages one of the teeth of the rack.

7. A ladder fitted with a device according to claim 1.

8. The ladder of claim 7, wherein one of the uprights is shorter than the other, and the device is fitted to the end of the shorter upright so that the longitudinal axes of the shorter upright and of the device coincide, the device being so proportioned that the slide of the device, when it is in fully retracted position, allows the ladder to be supported on even ground.

9. The ladder of claim 7, wherein the uprights are of equal length, and the device is strapped to an end of one upright by means of removable means.